The following description of the background of the invention is provided simply as an aid in understanding the invention and is not admitted to describe or constitute prior art to the invention.
The Epidermal Growth Factor receptor (EGFR; also known as HER1 or ErbB-1) is a transmembrane tyrosine kinase receptor expressed on epithelial cells that is strongly linked to several cancers, including but not limited to head and neck squamous cell carcinoma (HNSCC), non-small cell lung cancer (NSCLC), colorectal cancer (CRC), breast cancer, pancreatic cancer, and brain cancer. The EGFR is shed in both healthy patients and cancer patients and is detectable in their serum. Serum levels of EGFR in cancer patients are known to vary from EGFR levels measured in healthy controls.
The therapeutic antibodies cetuximab (Erbitux™) and panitumumab (Vectibix™) were developed for use as targeted therapies that recognize and inhibit the extracellular domain of EGFR. Cetuximab is approved by the FDA for use as an intravenous treatment for head and neck cancer and colorectal carcinoma, while panitumumab is approved by the FDA for use as a treatment for colorectal cancer.
Some patients have cancer that is resistant or becomes resistant to treatment with cetuximab or panitumumab (see Carney, Expert Rev Mol Diagn. 2007 May; 7(3):309-19; Wheeler, et al., Oncogene. 2008 Jun. 26; 27(28): 3944-3956; Bardelli, et al., J Clin Oncol. 2010 Mar. 1; 28(7):1254-61). Therefore it is desirable for doctors to monitor ongoing therapy to determine whether cancer cell resistance to the therapeutic antibodies is increasing, and modify the treatment accordingly. It is also desirable for doctors to determine whether all of the soluble EGFR is bound to the therapeutic antibodies.